Transplantation of osteoblasts to an affected area to repair a bone defect due to a bone tumor, trauma, osteomyelitis, or the like or a bone defect after curettage of a bone tumor or the like can be expected to promote bone formation and to improve functional and morphological prognosis. In actuality, treatment performed by autologous transplantation of bone marrow cells collected from, for example, the cancellous bone of a patient has been carried out, and the effectiveness of the treatment is known. In this case, osteoblasts obtained by differentiation induction from mesenchymal stem cells contained in autologous bone marrow cells are considered to contribute to bone formation and remodeling. Meanwhile, prevalence of osteoporosis has been increasing in step with the aging of the population, and bone fracture of an elderly person may lead to prolonged bed rest. Transplantation of osteoblasts is considered to be capable of promoting healing of bone fracture due to osteoporosis, trauma, or the like, intractable bone fracture, and pseudofracture. In addition, the transplantation of the osteoblasts may also be useful for, for example, rheumatoid arthritis, idiopathic osteonecrosis of the femoral head, arthrosis deformans, lumbar spondylosis deformans, spinal canal stenosis, disc herniation, spondylolysis, spondylolytic spondylolisthesis, scoliosis, cervical spondylotic myelopathy, ossification of posterior longitudinal ligament, spinal cord injury, coxarthrosis, gonarthrosis, slipped capital femoral epiphysis, osteomalacia, bone repair after surgery (such as breast bone repair after cardiac surgery), repair of a defect associated with artificial ankle joint surgery, osteomyelitis, and osteonecrosis.
On the other hand, a periodontal disease may be referred to as the fourth lifestyle-related disease, occurs at a very high prevalence in persons, and causes various systemic diseases. As the periodontal disease progresses, bone resorption of the alveolar bone occurs. Accordingly, when osteoblasts can be supplied to a local bone resorption site with high efficiency, the alveolar bone may be regenerated and treated.
When transplantation of osteoblasts is combined with bone transplantation, artificial bone transplantation, artificial joints, and implants, therapeutic effects may be enhanced.
Bone marrow mesenchymal stem cells, bone marrow cells including bone marrow mesenchymal stem cells, and the like have heretofore been used as such osteoblasts for transplantation. However, collection of the bone marrow has problems. For example, the collection is highly invasive to a patient and a sufficient number of bone marrow cells cannot be supplied in some cases. On the other hand, use of human embryonic stem cells (ES cells) does not require collection of the bone marrow from a patient and may supply a sufficient number of osteoblasts, but may cause a risk of tumorigenesis of residual ES cells after transplantation in addition to ethical issues. In addition, use of iPS cells does not require collection of the bone marrow from a patient and may supply a sufficient number of osteoblasts, but may cause a risk of tumorigenesis of residual iPS cells after transplantation.
In Non Patent Literature 1, there is a disclosure of introduction of a lentivirus vector including Osterix into human ES cells and differentiation induction into osteoblasts in an osteogenic medium.
In Non Patent Literature 2 and Non Patent Literature 3, there are disclosures of preparation of osteoblasts from mouse iPS cells through conversion into MSCs by differentiation induction in an osteogenic medium.
In Non Patent Literature 4, there is a disclosure of preparation of osteoblasts by introducing an adenovirus vector including Runx2 into mouse iPS cells and subjecting the cells to differentiation induction in an osteogenic medium.
As disclosed in Non Patent Literature 1 to Non Patent Literature 4, osteoblasts are prepared from pluripotent stem cells, such as ES cells and iPS cells, by differentiation induction, and hence the methods require long-term culture and have risks of carcinogenesis.
For example, the following reports have been made on the fact that, when a gene group of a tissue-specific transcription factor is introduced into somatic cells, direct differentiation induction into tissue cells can be achieved without conversion into iPS cells (direct reprogramming (direct conversion)):
mouse fibroblast→chondrocyte (SOX9+Klf4+c-Myc genes were introduced),
mouse fibroblast→cardiac muscle cell (GATA4+Mef2c+Tbx5 genes were introduced),
mouse fibroblast→liver cell (Hnf4α+(Foxa1, Foxa2, or Foxa3) genes were introduced),
mouse fibroblast→neural stem cell (for example, Sox2+FoxG1 genes were introduced), and
mouse or human cell→hematopoietic stem cell.
However, there is no report of direct conversion of the somatic cells into the osteoblasts.